应变式井下工程参数测量传感器组桥与布片研究

为了实时了解井下钻头的工作情况,提高钻井的安全性和可靠性,设计了一种应变式传感器。该传感器使用4组全桥方式的测量电桥。测量电桥采用科学的布片和组桥方法,能同时测量钻压、扭矩和钻头所受的侧向力,并有效抵消温度对测量参数的影响,从而降低各测量参数之间的耦合影响。针对井下恶劣的工况条件,采用了镍铬铝合金制作的金属箔式应变片。该应变片能够抗高温、抗蠕变和耐腐蚀。现场试验结果表明,各组测量电桥能够满足实际工况需要。     

Percolation and the resistive transition of the critical temperature Tc of Nb3Sn

The relationship between the distribution of the critical temperature, the percolation function, and the resistive transition of the critical temperature is explored for polycrystalline Nb₃Sn. In the neighborhood of the critical temperature, Nb₃Sn is assumed to be a random mixture of superconducting and normal grains. Percolation concepts are applied to a study of the resistivity. A general analysis is made showing that the onset and shape of the resistive transition for composite conductors are determined by the percolation function and the distribution of the critical temperature. An approximate form of the percolation function is determined based on a linear FEM analysis. Example resistive transitions are calculated for an assumed normal distribution of the critical temperature. An argument is presented that relates grain orientation and strain dependence in Nb₃Sn. It is noted that a dependence of the distribution of T_c with strain, in addition to the usual shift in T_c with strain, would be the result of a strain dependence that is a function of grain orientation. The analysis shows the extent to which the slope of the resistive transition is a measure of the distribution of the critical temperature, and therefore a measure of the grain orientation strain sensitivity. Finally, a method is described to determine the percolation function experimentally.     

Influence of Implicit Integration Scheme on Prediction of Shear Band Formation

Implicit integration schemes for elastoplastic constitutive equations have been developed in recent years as an alternative to explicit schemes. The consistent tangent constitutive matrix Dcon that results from implicit schemes makes the global stiffness matrix consistent with the implicit integration procedure and differs from the traditional continuum tangent constitutive matrix Dep that results from explicit schemes. Onset of strain localization and shear banding has been traditionally predicted using the continuum tangent constitutive matrix. It is shown that different criteria for onset of shear-band formation are obtained depending on whether Dcon or Dep is used. It is shown that shear band prediction using Dcon is step-size dependent, and that the use of Dcon influences the predicted onset of strain localization in frictional materials. An analytical equation for prediction of the onset of shear-band formation using Dcon for the Mohr–Coulomb model is developed, and a numerical example is presented.     

Compression testing of a sintered Ti6Al4V powder compact for biomedical applications

In this study, the compression deformation behavior of a Ti6Al4V powder compact, prepared by the sintering of cold compacted atomized spherical particles (100–200 μm) and containing 36–38% porosity, was investigated at quasi-static (1.6×10⁻³–1.6×10⁻¹ s⁻¹) and high strain rates (300 and 900 s⁻¹) using, respectively, conventional mechanical testing and Split Hopkinson Pressure Bar techniques. Microscopic studies of as-received powder and sintered powder compact showed that sintering at high temperature (1200 °C) and subsequent slow rate of cooling in the furnace changed the microstructure of powder from the acicular alpha () to the Widmanstätten (+β) microstructure. In compression testing, at both quasi-static and high strain rates, the compact failed via shear bands formed along the diagonal axis, 45° to the loading direction. Increasing the strain rate was found to increase both the flow stress and compressive strength of the compact but it did not affect the critical strain for shear localization. Microscopic analyses of failed samples and deformed but not failed samples of the compact further showed that fracture occurred in a ductile (dimpled) mode consisting of void initiation and growth in phase and/or at the /β interface and macrocracking by void coalescence in the interparticle bond region.     

Strain rate sensitivity of the commercial aluminum alloy AA5182-O

The mechanical behavior of the commercial aluminum alloy AA5182-O is investigated at temperatures ranging from −120 to 150 °C and strain rates from 10⁻⁶ to 10⁻¹ s⁻¹. The strain rate sensitivity parameter is determined as a function of temperature and plastic strain, and the strain rate and temperature range in which dynamic strain aging leads to negative strain rate sensitivity is mapped. The effect of dynamic strain aging on ductility and strain hardening is investigated. The sensitivity of the measured quantities to the experimental method employed and their dependence on grain shape are discussed. The experimental data are compared with the predictions of a model constructed based on a recently proposed mechanism for dynamic strain ageing. The mechanism is based on the effect solute clustering at forest dislocations has on the strength of dislocation junctions. The model is shown to reproduce qualitatively the experimental trends.     

Strain profiling of fatigue crack overload effects using energy dispersive X-ray diffraction

Synchrotron based energy dispersive X-ray diffraction has been used to profile the strains around fatigue cracks in 4140 steel test specimens. In particular strain field comparisons were made on specimens prepared: with initial constant stress intensity fatigue; with this initial fatigue followed by a single overload cycle; and with this fatigue-overload sequence followed by an additional constant stress intensity fatigue. The strain profiles behind, at and in-front-of the crack tip are discussed in detail. Selected strain profiles measurements under in situ applied tensile stress are also presented. The technique of optical surface height profiling reveals surface depression effects which can be correlated with the interior strain profiles.     

单片机在织机送经系统中的应用

本文阐述了如何提高织机送经机构送经均匀性的问题，重点对采用单片机控制织机送经系统的实现方案进行了论述，最后对单片机控制送经系统的运行情况及推广使用作了说明。     

一种新型光纤应变传感器的设计

本文提出了一种用于动态应变测量的新型光纤应变传感器，该系统由具有相位压缩功能的萨格纳克干涉仪构成，与普通干涉仪相比该系统的动态测量范围扩大了数百倍，并且系统不受外界缓变量的影响，信号处理电路简单易行。     

内压球壳大开孔接管区电阻应变测量中不确定度的评定

本文对内压球壳大开孔接管区电阻应变测量进行了测量不确定度的B类评定 ,发现其外壁应力测量相对标准不确定度一般不超过 2 % ,可满足实验应力分析要求     

复合材料层间应变测试实验

复合材料受到应力作用层间会产生变形,应力过大层间会出现撕裂的现象。针对这一问题, 利用光纤法珀应变传感器与复合材料层间间隙尺寸相当的特点,将该传感器置入复合材料层间,在万能拉伸仪上进行复合材料应变测试实验。实验表明:利用光纤法珀应变传感器检测复合材料层间应变的方法是完全可行的。